Recent developments in biotechnology have made biologically active macromolecules such as growth hormones available in large enough quantities to be considered for treating animals to obtain beneficial effects such as increased weight gains and increased milk production on a commercial scale.
Presently the administration of growth hormones to animals to obtain the above beneficial effects is accomplished by daily injection or periodic injection of compositions which deliver the hormone for extended periods of time such as those described in U.S. Pat. No. 4,452,775 teaching a cholesterol matrix delivery system for the sustained release of macro-molecules, including a variety of growth hormones. In actual practice and for convenience when hormone preparations are used, groups of animals are frequently injected with a stock preparation. It is therefore desirable to provide growth hormone compositions which contain antimicrobial preservatives such as antibacterial and antifungal agents to prevent mold, fungus and bacterial growth.
Unfortunately, due to the complex modes of action and intricate structures of biologically active macromolecules such as growth hormones many compounds which are normally used as preservatives interfere and/or interact with these hormones resulting in compositions which are either inactive or do not provide the expected level of biological response while other preservatives are not acceptable for use in animals which are used as a food source.
It is an object of this invention to provide growth hormone compositions containing preservatives which are suitable for use in animals to be used as a food source, retain the desired biological activity of the hormone and prevent the growth of fungus and/or bacteria.